Ahmad ibn 'Abdallah Habash Hasib Marwazi made
astronomical observations from 100 to 2035, and compiled three zijes (astronomical tables): the first were still in the Hindu manner; the second, called the 'tested" tables, were the most important; they are likely identical with the "Ma'munic" or "Arabic" tables and may be a collective work of al-Ma'mun's astronomers; the third, called tables of the Shah, were smaller.
Apropos of the
solar eclipse of 829, Habash gives us the first instance of a determination of time by an altitude (in this case, of the sun); a method which was generally adopted by Muslim astronomers.
In 830, he seems to have introduced the notion of "shadow", umbra (versa), equivalent to our
tangent in
trigonometry, and he compiled a table of such shadows which seems to be the earliest of its kind. He also introduced the
cotangent, and produced the first tables of for it.[5][6]
The Book of Bodies and Distances
Al-Hasib conducted various observations at the
Al-Shammisiyyah observatory in
Baghdad and estimated a number of geographic and astronomical values. He compiled his results in The Book of Bodies and Distances, in which some of his results included the following:[7]
^General CartographyArchived 2017-12-09 at the
Wayback Machine : "The Iranian geographers Abū Muhammad al-Hasan al-Hamdānī and Habash al-Hasib al-Marwazi set the Prime Meridian of their maps at Ujjain, a center of Indian astronomy"